1. Field of the Invention
The present invention relates to a system and method for reading two-dimensional images. More particularly, the present invention relates to a system and method for reading a two-dimensional images, such as fingerprints, signatures, and photographs, using an optical scanning head and a data compression algorithm.
2. Description of Related Art
Two-dimensional images are capable of carrying valuable information for use in various applications. For example, two-dimensional images may provide personal identification (e.g., by a fingerprint) or a record of, for example, a person""s medical history. Therefore, two-dimensional images are extremely valuable for carrying and conveying information and data.
Recently, optical scanners and readers have been developed that can capture and decode two-dimensional images. Such optical devices scan or obtain a video xe2x80x9cpicturexe2x80x9d of the two-dimensional image and process it using data compression techniques to obtain decoded data representative of the image. This data can then be used in comparing the two-dimensional image to some known data generated from a known image to determine whether the decoded data and known data match. The known data can be encoded in a two-dimensional barcode symbology representative of the known image.
Manipulation of data derived from two-dimensional images is useful in a number of applications. For example, when a person opens a bank account, the bank can scan the person""s fingerprint and decode that scanned image into data representative of the person""s fingerprint (xe2x80x9cstored dataxe2x80x9d), which is kept on file by the bank and by other institutions. Moreover, the stored data can be encoded onto a card that provides access to automatic teller machines (ATMs). When the person wants to gain access to money stored in an ATM, the person is asked to insert his or her ATM card into the ATM and place his or her fingertip in contact with a sensor-containing glass in which the contrast is controlled electronically in front of an optical scanner located at the ATM. The optical scanner scans and decodes the person""s fingerprint to obtain features (data) representative of the fingerprint (xe2x80x9cnew dataxe2x80x9d). This new data can then be compared to the stored data kept on file with the bank or obtained from the ATM card. If the new data matches the stored data, the person is given access to the ATM; if not, access is denied. The stored data can be encoded onto the ATM card by scanning the person""s fingertip and decoding the scanned information into a two-dimensional barcode symbology that represents the person""s fingerprint.
Conventional optical scanners for use with two-dimensional images are very expensive, however, due to the high cost of the components necessary to build such scanners. In conventional optical scanners for two-dimensional images, the most expensive component is the image sensor, which comprises a charge coupled device (CCD). Accordingly, using CCDs for two-dimensional image sensing renders this technology impractical for many applications.
Therefore, a need exists for a system and method for scanning and decoding two-dimensional images that employs a sensor that is much less expensive than a CCD sensor, that can perform data compression to process the image after scanning, and that can generate a barcode symbology representation of the processed image.
Accordingly, the present invention is directed to a system and method for scanning and decoding a two-dimensional image using an inexpensive optical scanning head that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
Additional features and advantages of the invention will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the system and method particularly pointed out in the written description and claims hereof, as well as the appended drawings.
To achieve these and other advantages, and in accordance with the purpose of the present invention, as embodied and broadly described herein, the invention is an optical scanning device and method for reading a two-dimensional image. The optical scanning device comprises a sensor for capturing the two-dimensional image and an LED array for projecting an emitted light towards the two-dimensional image, all of which are mounted on a printed circuit board. The LED array includes a plurality of LEDs with each of the LEDs being oriented to emit light at a non-zero angle with respect to a line running perpendicular to the front of the PCB and at an angle different from any of the other LEDs. The sensor also includes a lens system disposed forward of the LED array for focussing the emitted light at the target, which may be a two-dimensional image. The sensor further includes a CMOS (complementary metal-oxide-silicon) detector for detecting at least a portion of the light reflected from the two-dimensional image, the CMOS detector including a photodiode array for sensing the reflected light to obtain a sensed two-dimensional image, and a processor for processing the sensed two-dimensional image to obtain an electrical image signal. The processor, which may be a microprocessor or microchip, may incorporate software capability for automatic gain control, automatic exposure control, automatic black level control and automatic calibration. The optical scanning device further comprises a compressor for compressing the electrical image data, the compressor employing a compression algorithm to obtain compressed image data. The optical scanning device finally comprises a decoder for decoding the compressed image signal to obtain image data representative of the two-dimensional image.
In another aspect, the present invention is a system and method for comparing a new two-dimensional image to stored data representative of a known two-dimensional image. The system comprises a sensor for capturing the new two-dimensional image. The sensor includes an LED array for projecting an emitted light towards the two-dimensional image, the LED array including a plurality of LEDs, each of the LEDs being oriented to emit light at a non-zero angle with respect to a line running perpendicular to the front of the PCB on which the system components are mounted and at an angle different from any other of the LEDs. The sensor also includes a lens system disposed forward of a detector for focussing light reflected from the two-dimensional image target onto the detector. The sensor includes a CMOS detector for detecting at least a portion of the reflected light from the two-dimensional image, the CMOS detector including a photodiode array for sensing the reflected light to obtain a sensed two-dimensional image, and a processor for processing the sensed two-dimensional image to obtain an electrical image signal. The system also comprises a compressor for compressing the new electrical image data to obtain a compressed new image data, the compressor employing a compression algorithm. The system further comprises a decoder for decoding the compressed new image signal to obtain new image data representative of the new two-dimensional image. The system finally comprises a second processor for comparing the new image data to the stored data to determine if the new image data matches the stored data.
In still another aspect, the present invention is a system and method for comparing a new two-dimensional image to stored data representative of a known two-dimensional image. The system comprises a sensor for capturing the new two-dimensional image. The sensor includes an LED array for projecting an emitted light towards the targeted two-dimensional image, the LED array including LEDs, each of which is oriented to emit light at a non-zero angle with respect to a line perpendicular to the front of the PCB and angle different than the other LEDs. The emitted light can either be used to illuminate the target image or it can be focused to form a frame identifying the field of view of the sensor. A cylindrical lens system disposed forward of the LED array focusses the emitted light into a line of light. Depending upon the orientation of the cylindrical lens(es), a line may be formed to illuminate the target two-dimensional image within a field of view of said sensor so that a reflected light is reflected from the new two-dimensional image. Alternatively, a vertical orientation of the cylindrical lens(es) provides two vertical lines of light for framing the field of view to allow the user to aim the sensor at the target, and the target image is illuminated by ambient light. The sensor further comprises a CCD array for detecting a portion of the reflected light from the new two-dimensional image, the CCD array being disposed substantially rearward of the LED array. Finally, the sensor includes a first processor for generating a new electrical image signal in response to detecting the portion of the reflected light, the new electrical image signal comprising an analog representation of the new two-dimensional signal. The system further comprises a compressor for compressing the new electrical image signal to obtain a compressed new image signal, the compressor employing a compression algorithm. The system also comprises a decoder for decoding the compressed new image data to obtain new image data representative of the new two-dimensional image. Finally, the system comprises a second processor for comparing the new image data to the stored data to determine if the new image data matches the stored data.